Problem Statement

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Load Balancer - Problem Statement

Overview

Design a load balancing system that distributes incoming network traffic across multiple backend servers to ensure high availability, reliability, and optimal resource utilization. The system should support various load balancing algorithms, health checking, auto-scaling integration, and handle millions of requests per second.

Functional Requirements

Traffic Distribution

  • Load Balancing Algorithms: Round-robin, least connections, weighted, IP hash, least response time
  • Session Persistence: Sticky sessions for stateful applications
  • Traffic Splitting: A/B testing, canary deployments, blue-green deployments
  • Geographic Routing: Route based on client location
  • Protocol Support: HTTP/HTTPS, TCP, UDP, WebSocket

Health Checking

  • Active Health Checks: Periodic probes to backend servers
  • Passive Health Checks: Monitor actual traffic for failures
  • Custom Health Endpoints: Configurable health check URLs
  • Failure Detection: Automatic detection of unhealthy servers
  • Automatic Recovery: Re-add servers when healthy

SSL/TLS Termination

  • HTTPS Support: Terminate SSL/TLS at load balancer
  • Certificate Management: Automatic certificate renewal
  • SNI Support: Multiple certificates per load balancer
  • HTTP/2 and HTTP/3: Modern protocol support

Advanced Features

  • Rate Limiting: Limit requests per client
  • DDoS Protection: Mitigate attacks
  • Request Routing: Path-based, host-based routing
  • Connection Draining: Graceful server removal
  • Auto-Scaling Integration: Add/remove servers dynamically

Non-Functional Requirements

Performance

  • Throughput: 1M+ requests per second
  • Latency: <1ms overhead
  • Concurrent Connections: 100K+ per load balancer
  • New Connections: 10K/sec per load balancer

Scalability

  • Horizontal Scaling: Multiple load balancer instances
  • Backend Scaling: Support 1000+ backend servers
  • Geographic Distribution: Deploy globally

Reliability

  • Availability: 99.99% uptime
  • Failover: Automatic failover between load balancers
  • No Single Point of Failure: Redundant load balancers
  • Graceful Degradation: Continue with reduced capacity

Success Metrics

  • Availability: 99.99%+
  • Latency Overhead: <1ms
  • Even Distribution: <5% variance across backends
  • Health Check Accuracy: 99.9%+
  • Failover Time: <5 seconds

This problem statement establishes the foundation for designing a production-grade load balancing system.